How big are your molds? Mine are big enough to hold up to 4 pounds of soap, and the liners work very well in them.
Re: seepage: I do get a little seepage at the corners that sometimes (but definitely not always) reaches as far as the mold, and when it does, it never leaks
outside of the mold itself. Like DeeAnna mentioned you'd be surprised at how miniscule of an amount it is. If I were to gather up all the seepage, I reckon it's not much more than a 1/8th to 1/4th teaspoon amount all told when I've poured at thin trace, and practically nothing when I pour at medium-thick trace. If any soap happens to reach past the liner to the mold, it's no biggie. I just scrape it off at unmolding time with one of those tapered plastic scrapers you can buy at the grocery store for scraping food off of dirty dishes. It comes off very easily. The discoloration left behind doesn't bother me, and it hasn't hurt my molds in the least- they are still holding up great 12 years and counting.
IrishLass